This invention relates to a method of generating video scrambling control words for the line-by-line scrambling or descrambling of the video components of a television signal in which control data, having a rate which is low relative to that of the line rate of the television signal, is employed to control the generation of the video scrambling control word for each line of the video components. The invention also relates to a television receiver employing this method.
A method of the above type is disclosed in U.S. Pat. No. 4,070,693 where each line of the video components of a television signal is scrambled by cutting the line and by changing the cut-point for each line. This is done in a random manner by a locally generated random sequence at the transmission source and a corresponding random sequence locally generated in the television receiver. Both random sequences are periodically reset by control data at a rate which is low relative to that of the line rate of the television signal, which control data is transmitted with the television signal. Such a method provides a relatively secure scrambling system.